The present invention relates to an image forming apparatus that forms an image using a developer having a charging property.
Conventionally, in a laser printer, generally, light is irradiated onto a charged photosensitive element to expose a surface of the photosensitive element, and an electrostatic latent image is formed on the surface of the photosensitive element. Then, charged toner is adhered to the electrostatic latent image and thereby the electrostatic latent image is developed as a toner image. The developed toner image is transferred onto a sheet and an image is formed on the sheet.
In the laser printer, within a development unit that allows toner to be adhered to an electrostatic latent image, the toner is triboelectrically charged while the toner is agitated. Thus, every time the laser printer is used, toner remained in the development unit is damaged and as a result the charging property of the toner is degraded over time (see FIG. 1).
In view of this, there is a laser printer that adds up the frequencies of use of the laser printer (e.g., the number of printed sheets or the driving hours of a development unit) and determines, based on a result of the adding up, degradation of the charging property of toner (see Japanese Patent Application Laid-Open No. 10-186861(1998), for example).